The Full Globin Repertoire of Turtles Provides Insights into Vertebrate Globin Evolution and Functions.

Schwarze K, Singh A, Burmester T - Genome Biol Evol (2015)

Bottom Line:
The globin E gene was selectively lost in the green anole, and the genes coding for globin X and globin Y were deleted in chicken.Histochemical analyses showed high levels of globin E in the pigment epithelium of the eye.Globin E probably has a myoglobin-like role in transporting O2 across the pigment epithelium to supply in the metabolically highly active retina.

evv114-F8: Distribution of globins among the vertebrate tree of life. *1. Absent in some icefish species (Sidell et al. 1997; di Prisco et al. 2002). *2 only in platypus (Hardison 2008).

Mentions:
The distribution of globins among gnathostome vertebrates shows a patchy pattern (fig. 8), which suggests that multiple independent losses of globin genes occurred during the evolution of most taxa (Hoffmann et al. 2011; Storz et al. 2011; Burmester and Hankeln 2014). The loss of certain globin genes may be partly explained by physiological changes that rendered the function of specific globins unnecessary. Other explanations for this pattern may include random changes of the genomes. When we ignore paraphyletic Hb and GbX isoforms (Dickerson and Geis 1983; Opazo, Hoffmann et al. 2015; Opazo, Lee, et al. 2015), the turtles (this study) and the coelacanth (Schwarze and Burmester 2013) are the only known vertebrates with all eight types of gnathostome globins. Notably, both turtles and the coelacanth are morphologically highly conserved taxa that have changed little during the Neozoic period. Furthermore, analyses of the coelacanth and the turtle genomes revealed comparably slow molecular evolution rates (Amemiya et al. 2013; Shaffer et al. 2013). Of course it is difficult to trace the physiological changes of these lineages throughout evolution; however, they did not affect the globin genes and thus the full set of globins had been inherited from the last common ancestor.Fig. 8.—

evv114-F8: Distribution of globins among the vertebrate tree of life. *1. Absent in some icefish species (Sidell et al. 1997; di Prisco et al. 2002). *2 only in platypus (Hardison 2008).

Mentions:
The distribution of globins among gnathostome vertebrates shows a patchy pattern (fig. 8), which suggests that multiple independent losses of globin genes occurred during the evolution of most taxa (Hoffmann et al. 2011; Storz et al. 2011; Burmester and Hankeln 2014). The loss of certain globin genes may be partly explained by physiological changes that rendered the function of specific globins unnecessary. Other explanations for this pattern may include random changes of the genomes. When we ignore paraphyletic Hb and GbX isoforms (Dickerson and Geis 1983; Opazo, Hoffmann et al. 2015; Opazo, Lee, et al. 2015), the turtles (this study) and the coelacanth (Schwarze and Burmester 2013) are the only known vertebrates with all eight types of gnathostome globins. Notably, both turtles and the coelacanth are morphologically highly conserved taxa that have changed little during the Neozoic period. Furthermore, analyses of the coelacanth and the turtle genomes revealed comparably slow molecular evolution rates (Amemiya et al. 2013; Shaffer et al. 2013). Of course it is difficult to trace the physiological changes of these lineages throughout evolution; however, they did not affect the globin genes and thus the full set of globins had been inherited from the last common ancestor.Fig. 8.—

Bottom Line:
The globin E gene was selectively lost in the green anole, and the genes coding for globin X and globin Y were deleted in chicken.Histochemical analyses showed high levels of globin E in the pigment epithelium of the eye.Globin E probably has a myoglobin-like role in transporting O2 across the pigment epithelium to supply in the metabolically highly active retina.